Abstract
Air separation is very important from the viewpoint of the economic and environmental advantages. In this work, defect-free facilitated transport membranes based on poly(amide-12-b-ethylene oxide) (Pebax-2533) and tetra(p-methoxylphenyl)porphyrin cobalt chloride (T(p-OCH3)PPCoCl) were fabricated in systematically varied compositions for O2/N2 separation. T(p-OCH3)PPCoCl was introduced as carriers that selectively and reversibly interacted with O2 and facilitated O2 transport in the membrane. The T(p-OCH3)PPCoCl had good compatibility with the Pebax-2533 via the hydrogen bond interaction and formed a uniform and thin selective layer on the substrate. The O2 separation performance of the thin film composite (TFC) membranes was improved by adding a small amount of the T(p-OCH3)PPCoCl and decreasing the feed pressure. At the pressure of 0.035 MPa, the O2 permeability and O2/N2 selectivity of the 0.6 wt % T(p-OCH3)PPCoCl/Pebax-2533 was more than 3.5 times that of the Pebax-2533 TFC membrane, which reached the 2008 Robeson upper bound. It provides a candidate membrane material for O2/N2 efficient separation in moderate conditions.
Highlights
Air separation is an essential process, in which the obtained oxygen-enriched air can be used to assist combustion by increasing the burning velocities [1], regenerate catalysts in the fluid catalytic cracking [2], and improve indoor air quality [3]; the obtained nitrogen-enriched air can be applied in keeping food fresh, preventing fires, oil recovery, and draining water [4,5]
Polymeric membranes are usually applied for air separation, but their gas separation performance is always limited by the Robeson upper bound between O2 permeability and O2 /N2 selectivity [12]
We developed a novel thin-film composite (TFC) membrane for O2 /N2 separation, which was fabricated using the cobalt porphyrin (T(p-OCH3 )PPCoCl) as the oxygen carrier, Pebax-2533 as the polymer matrix, and macroporous PVDF as the support
Summary
Air separation is an essential process, in which the obtained oxygen-enriched air can be used to assist combustion by increasing the burning velocities [1], regenerate catalysts in the fluid catalytic cracking [2], and improve indoor air quality [3]; the obtained nitrogen-enriched air can be applied in keeping food fresh, preventing fires, oil recovery, and draining water [4,5]. Pressure swing adsorption (PSA) is another commonly used air separation method that can produce high purity (≈95%) oxygen with medium production, but the larger space, higher investment, and energy consumption of the process are still challenging [7]. Compared with these air separation technologies, the membrane gas separation method is a green and sustainable process because of its continuous production, easy operation, small space, environmental friendliness, Membranes 2019, 9, 115; doi:10.3390/membranes9090115 www.mdpi.com/journal/membranes.
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